The present invention relates to novel monolithic ceramic materials using modified hydrogen silsesquioxane resin. These materials can be formed into complex shapes which have good oxidation resistance at high temperatures and high strength.
The formation of ceramics using siloxane polymers is known in the art. For instance, U.S. Pat. No. 4,888,376 describes the use of an organopolysiloxane as a binder for silicon carbide powder. The organopolysiloxanes and the resultant ceramics described therein, however, are different than modified hydrogen silsesquioxane resin and its ceramic in that the chars of the reference are carbon rich compared to chars of the present invention which have the generic formula SiO.sub.y C.sub.z, wherein y=1.2 to 1.6 and z=0.2-0.6.
Similarly, Leung et al. teach carbon-containing black glass monoliths derived from organopolysiloxanes. The organopolysiloxanes taught therein, however, are limited to cyclosiloxanes and, thus, do not encompass the modified hydrogen silsesquioxane resin claimed herein.
Hydrogen silsesquioxane resin is also known in the art. For instance, Collins et al. in U.S. Pat. No. 3,615,272 describe the production of soluble hydrogen silsesquioxane resin by the hydrolysis and condensation of a silane in a sulfuric acid medium. Similarly, Haluska et al. U.S. Pat. No. 4,756,977 teach the use of hydrogen silsesquioxane resin to form protective ceramic coatings on electronic devices. These references, however, do not describe the modification of the resin nor its use in forming monolithic bodies.
The present inventors have unexpectedly found that modified hydrogen silsesquioxane resin can be used to prepare ceramics with excellent properties.